1. Field of the Invention
The invention is generally related to the area of optical systems and devices. In particular, the invention is related to micro-optic devices and the method of making the same. More particularly, the invention is related to techniques of obtaining low-loss coupling optics, packaging structure and process to secure components constituting a micro-optic fiber device.
2. The Background of Related Art
The most commonly used approach to making a micro-optic fiber device is to make two fiber collimators separately and then insert one or more optical processing elements such as WDM filters, isolator cores, polarization beam combiners, circulator cores in between. In a typical prior art assembly process, the optical processing elements are attached to either the first collimator or the second collimator by using soldering or epoxy bonding. The resultant sub-assembly is then aligned and bonded with the other collimator. FIG. 1 shows a traditional soldering structure. There are two additional sleeves 106 and 20 used to hold two collimators and link them together with an outer housing by soldering.
With soldering, the devices built suffer from high thermal-dependent loss and insertion loss due to residual stress. With traditional epoxy bonding, epoxy can flow into the optical path, resulting in bad optical performance and poor reliability.
FIG. 2 replicates FIG. 2 of U.S. Pat. No. 6,282,339 in which a dual fiber collimator and a single fiber collimator are used to make a WDM device. A WDM filter is first attached to a GRIN lens of the first collimator. Then the sub-assembly is inserted into a first glass tube and fixed. A dual fiber pigtail is then aligned with this sub-assembly to the minimum reflection loss and then connected to the sub-assembly through a second glass tube, resulting in a dual fiber collimator. For the transmission side, a secondary GRIN lens and a single fiber pigtail are inserted and glued in a third glass tube, and a fourth glass tube, respectively. Two glass tubes are fixed by their end-faces after being aligned with the dual fiber collimator. Finally, two collimators are aligned and bonded at the glass tube end-faces. The structure is simple but not stable with temperature change, especially on the dual fiber collimator side. The gap between the dual-fiber pigtail and the GRIN lens cannot be too small in the configuration, leading to a high defocusing loss.
The present disclosure provides a cost-effective and low loss solution to overcome at least these issues identified in the prior art. The reflection low loss is achieved by minimizing the defocusing of an optical lens (e.g., a GRIN lens). The transmission loss is minimized by using a matching lens with the GRIN lens.